1. Field of the Invention
The invention relates to the field of disk drives used as storage devices in computers. More specifically, the invention relates to a preseed layer for a magnetic disk used in a disk drive.
2. Description of the Background Art
Disk drives using magnetic recording of digital information are used to store most of the information in contemporary computer systems. A disk drive typically has a housing with at least one rotatable magnetic disk having a plurality of concentric tracks of magnetically stored data. There is at least one recording head typically with a separate write element and read element for writing and reading data on the tracks. The recording head is constructed on a slider and the slider is attached to a suspention. The suspension is connected to an actuator which positions the recording head over a specific track of interest. The actuator first rotates to seek the track of interest and after positioning the recording head over that track maintains the recording head in close registration to that track.
The slider carrying the recording head has a disk facing surface upon which an air bearing is constructed. The purpose of the air bearing is to allow the slider to float on a cushion of air over the rotating disk and to be positioned close to the disk surface. Alternatively, the disk facing surface of the slider may be designed to be in contact with the disk.
The magnetic recording disk in a disk drive typically has a substrate, an underlayer usually of chromium or a chromium alloy, a magnetic layer usually of a cobalt alloy, and an overcoat of carbon. The substrate is typically formed of glass or aluminum alloy. The microstructural aspects of the magnetic layer such as crystallographic orientation, grain size, and the degree of magnetic exchange coupling play key roles in the recording performance of the disk and are strongly influenced by aspects of the underlayer. One example of demonstrating the role that the underlayer plays is given in U.S. Pat. No. 5,789,056, Bian, et al., which is incorporated by reference herein.
Each new disk drive product usually has a higher areal recorded density of information than previous products. As the recorded bit on the disk becomes smaller and smaller, there is a greater demand placed on the necessary disk magnetic performance to achieve those high densities. Typically, the disk in each new disk drive product is required to have a higher signal to noise ratio and the ability to record sharper magnetic transitions. While previous disks have had adequate performance for the lower required densities of previous disk drives, the performance of disks needs to be improved for the very high density requirements demanded for new disk drives. Even a small improvement in signal to noise ratio may have a significant impact on the recording performance of the disk.
From the foregoing, it is apparent that a disk with improved recording characteristics is needed. In particular, disks with improved underlayers which result in better magnetic recording performance are needed.
The present invention provides for a disk for magnetic recording having a preseed layer comprising chromium, titanium, and yttrium. This particular preseed layer unexpectedly provides for a more sharply defined preferred orientation in the magnetic layer. Using this preseed layer results in a disk with better signal to noise ratio and narrower readback pulses. In addition, the present invention provides for a disk drive wherein the disk includes a preseed layer comprising chromium, titanium, and yttrium.
Additional advantages of the present invention will become apparent to those skilled in this art from the following detailed description along with the accompanying illustrations wherein only the preferred embodiment of the invention is shown. The invention is capable of other embodiments, and its details are capable of modifications in various obvious respects without parting from the scope of the invention.